Various membrane-bound receptor molecules are undoubtedly important in the regulation of the immune response by T-lymphocytes. The goal of these studies is to identify and structurally characterize these receptor molecules and the ligands with which they interact. Project areas include: (1) studies on the primary structure of (glyco) proteins associated with the T3 and T8 complexes, (2) identification of the target antigens of two human cytotoxic T cell clones specific for class II molecules and (3) attempts to obtain a stable, quantitative source of homogeneous T-cell receptors by preparing T-cell hybridomas.